date Subquery PHP and Mysql - mysql

Question

Following is my sql query with included subquery. Essentially I'm looking to obtain the most recent meter readings for our equipment for a given month and year. I know it's in my subquery where the issue is coming up but I don't know how to properly fix it.
Following is result if I delete the subquery and just select equipment with meter readings for that month.
eid eqid name pid hours date
70 C1 KOMATSU WA250 3YD BUCKET 27 1176 2013-10-07
70 C1 KOMATSU WA250 3YD BUCKET 27 1195 2013-10-28
70 C1 KOMATSU WA250 3YD BUCKET 27 1178 2013-10-14
73 C11 KOMATSU PC200 EXCAVATOR 27 1080 2013-10-14
73 C11 KOMATSU PC200 EXCAVATOR 27 1099 2013-10-28
73 C11 KOMATSU PC200 EXCAVATOR 27 1078 2013-10-07
92 C4 CATERPILLAR 304D MINI EX 27 646 2013-10-14
92 C4 CATERPILLAR 304D MINI EX 27 645 2013-10-07
92 C4 CATERPILLAR 304D MINI EX 27 649 2013-10-28
58 E14 BOBCAT-ATV 2300 Utility 8 522 2013-10-31
61 E17 SKYTRAK FORKLIFT 40 943 2013-10-10
62 E18 SKYTRAK FORKLIFT 5 1790 2013-10-30
62 E18 SKYTRAK FORKLIFT 5 1789 2013-10-29
62 E18 SKYTRAK FORKLIFT 5 1777 2013-10-13
62 E18 SKYTRAK FORKLIFT 5 1772 2013-10-07
62 E18 SKYTRAK FORKLIFT 5 1777 2013-10-13
62 E18 SKYTRAK FORKLIFT 5 1772 2013-10-04
62 E18 SKYTRAK FORKLIFT 5 1772 2013-10-07
62 E18 SKYTRAK FORKLIFT 5 1772 2013-10-04
67 E23 BOBCAT SKID STEER 27 1178 2013-10-28
Following is result of full query including subquery.
92 C4 CATERPILLAR 304D MINI EX 27 649 2013-10-28
61 E17 SKYTRAK FORKLIFT 40 943 2013-10-10
62 E18 SKYTRAK FORKLIFT 5 1790 2013-10-30
Following is query I am using.
SELECT e.eid, e.eqid, e.name, m.pid, m.hours, m.date FROM meter m
JOIN equipment e ON m.eid = e.eid
WHERE MONTH(date) = $month
AND YEAR(date) = $year
AND m.date = (SELECT MAX(m2.date) FROM meter m2 WHERE m2.eid = m.eid)
ORDER BY e.eqid ASC
Any help is greatly appreciated.
EDIT***
I would have never gotten there Sebas. I had to change one thing and it worked perfectly.
SELECT DISTINCT e.eid, e.eqid, e.name, m.pid, m.hours, m.date
FROM equipment e
JOIN (
SELECT eid, MAX(date) as date
FROM meter
WHERE MONTH(date) = $month
AND YEAR(date) = $year
GROUP BY eid
) maxdate ON maxdate.eid = e.eid
JOIN meter m ON m.eid = e.eid AND m.date = maxdate.date
ORDER BY e.eqid ASC

Answer 1

Guessing out the fields of each table, I figured the following query:
SELECT DISTINCT e.eid, e.eqid, e.name, m.pid, m.hours, m.date
FROM
equipment e
JOIN (
SELECT eid, MAX(date) date
FROM meter
WHERE
MONTH(date) = $month
AND YEAR(date) = $year
GROUP BY eid
) maxdate ON maxdate.eid = e.eid
JOIN meter m ON m.eid = e.eid AND m.date = maxdate.date
ORDER BY e.eqid ASC

Answer 2

Try
SELECT e.eid, e.eqid, e.name, m.pid, m.hours, m.date
FROM
(
SELECT eid, MAX(date) date
FROM meter
WHERE date BETWEEN '2013-10-01' AND LAST_DAY('2013-10-01')
GROUP BY eid
) q JOIN meter m
ON q.eid = m.eid
AND q.date = m.date JOIN equipment e
ON q.eid = e.eid
ORDER BY e.eid
Note: make sure you have an index on date. Don't apply any functions (MONTH() and such) to this columns in WHERE clause because it prevents from using any index you might have on it effectively causing full table scan.
Sample output:
| EID | EQID | NAME | PID | HOURS | DATE |
|-----|------|--------------------------|-----|-------|------------|
| 58 | E14 | BOBCAT-ATV 2300 Utility | 8 | 522 | 2013-10-31 |
| 61 | E17 | SKYTRAK FORKLIFT | 40 | 943 | 2013-10-10 |
| 62 | E18 | SKYTRAK FORKLIFT | 5 | 1790 | 2013-10-30 |
| 67 | E23 | BOBCAT SKID STEER | 27 | 1178 | 2013-10-28 |
| 70 | C1 | KOMATSU WA250 3YD BUCKET | 27 | 1195 | 2013-10-28 |
| 73 | C11 | KOMATSU PC200 EXCAVATOR | 27 | 1099 | 2013-10-28 |
| 92 | C4 | CATERPILLAR 304D MINI EX | 27 | 649 | 2013-10-28 |
Here is SQLFiddle demo